1. Field of the invention
The present invention relates to a road for guiding an automatically driven motor vehicle, wherein the road is provided with a linear array of magnetic information sources arranged therein at predetermined intervals. The present invention also concerns a driving method on such a road, using an automatically driven vehicle having magnetic sensors for detecting the magnetic information sources.
2. Description of the Related Art
It has heretofore been contemplated to provided an automated vehicle control system, for automatically controlling a driven motor vehicle at a predetermined position in a parking lot, as well as an automatic motor vehicle system for driving an automatically driven motor vehicle on a highway.
As one type of automatic motor vehicle running system, there is known the automated highway system which is presently being conducted under the authority of the Ministry of Construction in Japan.
In such a system, an automatically driven motor vehicle runs on a specialized road which is installed with magnetized nails therein. The vehicle is automatically driven by detecting its own vehicle posture based on a direction in which the magnetized nails are installed. Such a system is referred to as an automatic driving road system.
Prior art which relates to the automatic driving road system appears in U.S. patent application Ser. No. 08/739,524. In this document, an automatically driven motor vehicle, including a magnetic sensor, is driven by detecting magnetic information sources disposed in a road and installed therein at substantially regular intervals, for example, at one meter intervals. More specifically, magnetized nails are buried in the center of the road, arranged so as to have the same magnetic polarity according to a desired driving direction.
Using such prior art, therefore, one is basically capable of ascertaining vehicle speed, and the like, by counting the magnetic information sources. Also, by means of magnetic sensors installed in both front and rear positions of the vehicle, one can detect the vehicle posture with respect to the magnetic information sources. In other words, one's posture with respect to the road, i.e. a yaw angle, is determined based on the respective intensities of magnetic fields detected by the two magnetic sensors which detect the magnetic information sources. Further, the road itself provides an NS (north-south) bit train for indicating section information of the road, which is made up of N-polarity magnetic sources and S-polarity magnetic sources, intermixed appropriately at predetermined distances, for example, at every 500 meters, thereby indicating section information of the road. Insofar as it is possible to detect such section information, the vehicle can be corrected for travel distance as well as to position itself on the road accordingly.
However, the road installed with magnetic information sources, as described above, does not have branching sections therein; that is, it is simply a straight non-forking road. However, normally roads, and highways for example, typically include portions therein where one road branches off from the main road. A problem arises, therefore, in how to implement and detect magnetic sources within a branching portion of a road, as well as how to arrange the structure of a portion of a road which includes a branch point therein.